{
 "cells": [
  {
   "cell_type": "markdown",
   "id": "44633740",
   "metadata": {},
   "source": [
    "-------\n",
    "* 记录人（学习人）：何明诗\n",
    "* 时间：2021-11-29\n",
    "* week14\n",
    "* 学习线上资源[python文档](www.python.com)\n",
    "-------"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "dde3ceb1",
   "metadata": {},
   "source": [
    "# 本周学习目标\n",
    "> 1. 函数的定义\n",
    "> 2. 函数的使用\n",
    "> 3. 函数的参数"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "209175e9",
   "metadata": {},
   "source": [
    "## 函数的定义\n",
    "* 定义一个函数的一般步骤"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "9382ca2a",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0 1 1 2 3 5 8 13 21 34 55 89 \n"
     ]
    }
   ],
   "source": [
    "a, b = 0, 1\n",
    "while a < 100:\n",
    "    print(a, end=' ')\n",
    "    a, b = b, a+b\n",
    "print()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "940f3c12",
   "metadata": {},
   "outputs": [],
   "source": [
    "# ...我想重复使用某一个功能（避免重复造轮子）\n",
    "# ...使用的人可以不懂代码，只要会调用函数即可 function_name()"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "0ae7d7bc",
   "metadata": {},
   "source": [
    "> 1. 定义函数的一般方法  \n",
    "\n",
    "...\n",
    "\n",
    "def function_name():# 1.function_name 遵循变量定义的规则 ==> f(x) python的函数可以自定义名称\n",
    "     \"\"\"函数的注释\"\"\" # 2.函数的注释可以和使用者交流\n",
    "     函数体          # 3.函数体要和定义函数保持一定的tab缩进\n",
    "     \n",
    "..."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "id": "62ed34e9",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "0 1 1 2 3 5 8 \n"
     ]
    }
   ],
   "source": [
    "def fib(n):    # write Fibonacci series up to n\n",
    "     \"\"\"Print a Fibonacci series up to n.\"\"\"\n",
    "a, b = 0, 1\n",
    "while a < 10:\n",
    "    print(a, end=' ')\n",
    "    a, b = b, a+b\n",
    "print()        "
   ]
  },
  {
   "cell_type": "markdown",
   "id": "c28c255d",
   "metadata": {},
   "source": [
    "## 函数的使用"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "id": "65171ba4",
   "metadata": {},
   "outputs": [],
   "source": [
    "fib(10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "id": "63fa34d6",
   "metadata": {},
   "outputs": [],
   "source": [
    "# 写一个函数 实现 hello world\n",
    "# 写一个函数 实现 hello username"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "id": "11506709",
   "metadata": {},
   "outputs": [],
   "source": [
    "def hello():\n",
    "    \"\"\"打印你好，世界\"\"\"\n",
    "    print(\"hello world\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "id": "c4d5381b",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "hello world\n"
     ]
    }
   ],
   "source": [
    "hello()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "id": "1bb53f9f",
   "metadata": {},
   "outputs": [],
   "source": [
    "def hello_user(username):\n",
    "    \"\"\"打印你好，同学\"\"\"\n",
    "    print(\"你好，\"+ username.title()+\"同学\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "id": "3b7c7906",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "你好，Jack同学\n"
     ]
    }
   ],
   "source": [
    "hello_user(\"jack\")"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "187a8736",
   "metadata": {},
   "source": [
    "* 思考：函数是否必须有参数？\n",
    "* 注意：\n",
    "> 1. 在第一行定义函数中，不需要任何信息就能完成工作，因此括号是空的（即便如此，括号必不可少！）  \n",
    "> 2. 要调用函数，可以依次指定函数名以及括号括起的必要信息。在第五行代码中，因为此函数greet_uesr()括号中不需要任何信息，只需要输入greet_uesr（）即可。和预期效果一样，打印Hello！：  "
   ]
  },
  {
   "cell_type": "markdown",
   "id": "fee13946",
   "metadata": {},
   "source": [
    "## 函数的参数\n",
    "\n",
    "> 1. 形式参数：定义函数时，写在 function_name 括号里面的参数\n",
    ">> 1. 在定义函数时，形式参数不占用空间\n",
    "\n",
    "> 2. 实际参数: 调用函数时，写在 function_name 括号里面的参数\n",
    ">> 2. 在使用函数时，形式参数被分配空间，变为实际参数"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "id": "aed2e65a",
   "metadata": {},
   "outputs": [],
   "source": [
    "def describe_pet(animal_type,pet_name):  # animal_type,pet_name只是形式参数\n",
    "    \"\"\"显示宠物信息\"\"\"\n",
    "    print(\"\\nI have a\" + animal_type + \".\")\n",
    "    print(\"My\" + animal_type + \"'s name is \"+pet_name.title() + \".\")\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "id": "1a178f36",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\n",
      "I have adog.\n",
      "Mydog's name is 豆豆.\n"
     ]
    }
   ],
   "source": [
    "describe_pet(\"dog\",\"豆豆\")  # \"dog\",\"豆豆\"实际参数"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "id": "833de4f3",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\n",
      "I have a豆豆.\n",
      "My豆豆's name is Dog.\n"
     ]
    }
   ],
   "source": [
    "describe_pet(\"豆豆\",\"dog\")"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "8224aece",
   "metadata": {},
   "source": [
    "* 当函数具有多个参数时\n",
    " > 1. 位置参数\n",
    ">> 1.形式参数有先后顺序，函数调用过程中应考虑参数的先后顺序，避免出现顺序错误的笑话\n",
    ">> 2.调用函数过程中要考虑形式参数的个数\n",
    " > 2.关键字参数\n",
    ">> 1.调用函数时，通过赋值的方式传递给形参数据\n",
    ">> 2.关键字参数不考虑先后顺序，因为是指定变量赋值\n",
    " > 3. 默认参数\n",
    ">> 1.在形式参数中，提前预先设置一个用户可能使用的参数值\n",
    ">> 2.用户在使用/调用函数时，可以省略不给磨人参数赋值\n",
    ">> 3.用户给默认参数赋值，将替换默认参数的值"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "bc1c0024",
   "metadata": {},
   "outputs": [],
   "source": [
    "def describe_pet(animal_type,pet_name):  # animal_type,pet_name只是形式参数\n",
    "    \"\"\"显示宠物信息\"\"\"\n",
    "    print(\"\\nI have a\" + animal_type + \".\")\n",
    "    print(\"My\" + animal_type + \"'s name is \"+pet_name.title() + \".\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "fc366532",
   "metadata": {},
   "outputs": [],
   "source": [
    "# 在使用describe_pet（）函数时 需要考虑 参数的位置， 从而进行参数数据的输入（实际参数的调用）\n",
    "\n",
    "describe_pet(\"dog\",\"豆豆\") # 要根据 形式参数的位置先后顺序 先写animal_type，再写pet_name"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 24,
   "id": "cc4c0157",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\n",
      "I have adog.\n",
      "Mydog's name is 豆豆.\n"
     ]
    }
   ],
   "source": [
    "# 关键字参数使用\n",
    "\n",
    "describe_pet(pet_name=\"豆豆\",animal_type=\"dog\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "id": "c60d96ad",
   "metadata": {},
   "outputs": [],
   "source": [
    "# 默认参数\n",
    "def describe_pet(pet_name,animal_type=\"dog\"):  # animal_type,pet_name只是形式参数\n",
    "    \"\"\"显示宠物信息\"\"\"\n",
    "    print(\"\\nI have a\" + animal_type + \".\")\n",
    "    print(\"My\" + animal_type + \"'s name is \"+pet_name.title() + \".\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 26,
   "id": "c8c09dff",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\n",
      "I have adog.\n",
      "Mydog's name is 豆豆.\n"
     ]
    }
   ],
   "source": [
    "describe_pet(\"豆豆\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 27,
   "id": "9756a243",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "hello\n"
     ]
    }
   ],
   "source": [
    "print(\"hello\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 28,
   "id": "f1fe5070",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Help on built-in function print in module builtins:\n",
      "\n",
      "print(...)\n",
      "    print(value, ..., sep=' ', end='\\n', file=sys.stdout, flush=False)\n",
      "    \n",
      "    Prints the values to a stream, or to sys.stdout by default.\n",
      "    Optional keyword arguments:\n",
      "    file:  a file-like object (stream); defaults to the current sys.stdout.\n",
      "    sep:   string inserted between values, default a space.\n",
      "    end:   string appended after the last value, default a newline.\n",
      "    flush: whether to forcibly flush the stream.\n",
      "\n"
     ]
    }
   ],
   "source": [
    "help(print)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "7247eedb",
   "metadata": {},
   "source": [
    "-----------\n",
    "参数使用过程中的思考与问题  \n",
    "> 1.思考：关键字参数 和 位置参数 是否可以一起使用？（可以）  \n",
    " >> 1.positional argument follows keyword argument(位置参数均要放在关键字参数前面）  \n",
    " >> 2. test1() got multiple values for argument 'x'(映射，不能出现multiple values(多重值））  \n",
    "> 2.定义函数：默认参数和非默认参数的先后关系  \n",
    " >> 1.non-default argument follows default argument(非默认参数均要放在默认参数前面）  \n",
    "\n",
    "\n",
    "-----------"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 31,
   "id": "8077d067",
   "metadata": {},
   "outputs": [],
   "source": [
    "# 案例一：\n",
    "def test1(x,y,z):\n",
    "    \"\"\"打印x,y,z的值\"\"\"\n",
    "    print(x)\n",
    "    print(y)\n",
    "    print(z)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 32,
   "id": "945ebd14",
   "metadata": {},
   "outputs": [
    {
     "ename": "SyntaxError",
     "evalue": "positional argument follows keyword argument (<ipython-input-32-fd583303ea9b>, line 1)",
     "output_type": "error",
     "traceback": [
      "\u001b[0;36m  File \u001b[0;32m\"<ipython-input-32-fd583303ea9b>\"\u001b[0;36m, line \u001b[0;32m1\u001b[0m\n\u001b[0;31m    test1(x=2,3,z=4)\u001b[0m\n\u001b[0m              ^\u001b[0m\n\u001b[0;31mSyntaxError\u001b[0m\u001b[0;31m:\u001b[0m positional argument follows keyword argument\n"
     ]
    }
   ],
   "source": [
    "test1(x=2,3,z=4)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 33,
   "id": "9ada8ab4",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "2\n",
      "3\n",
      "4\n"
     ]
    }
   ],
   "source": [
    "test1(2,z=4,y=3)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 34,
   "id": "d9cfc198",
   "metadata": {},
   "outputs": [
    {
     "ename": "TypeError",
     "evalue": "test1() got multiple values for argument 'x'",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-34-abf767fdec53>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mtest1\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;36m2\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0mx\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;36m3\u001b[0m\u001b[0;34m,\u001b[0m\u001b[0my\u001b[0m\u001b[0;34m=\u001b[0m\u001b[0;36m1\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;31mTypeError\u001b[0m: test1() got multiple values for argument 'x'"
     ]
    }
   ],
   "source": [
    "test1(2,x=3,y=1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 38,
   "id": "1b88560c",
   "metadata": {},
   "outputs": [],
   "source": [
    "# 案例二：\n",
    "def test1(x,z,y=3):\n",
    "    \"\"\"打印x,y,z的值\"\"\"\n",
    "    print(x)\n",
    "    print(y)\n",
    "    print(z)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "1ec5d84b",
   "metadata": {},
   "source": [
    "## 课本练习实践\n",
    "> 1.请大家总结函数的优势  \n",
    "> 2.预习课本第四章函数与模块  \n",
    ">> 1. 完成课本元音字母实践\n",
    ">> 2. 浏览模块，创建模块和调用模块，了解PEB 8 python国际代码标准"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 39,
   "id": "955e6882",
   "metadata": {},
   "outputs": [],
   "source": [
    "def search4vowels(word):\n",
    "    \"\"\"判断输入文本出现的元音字母有哪些\"\"\"\n",
    "    vowels = set(\"aeiou\")\n",
    "    word = set(word)\n",
    "    print(vowels & word)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 40,
   "id": "1f2168fb",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "{'i', 'e', 'a'}\n"
     ]
    }
   ],
   "source": [
    "search4vowels(\"jdijdiiaei\")"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "66163c8f",
   "metadata": {},
   "source": [
    "# 下周预告\n",
    "## 函数返回值\n",
    "## 模块介绍"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "c33440ce",
   "metadata": {},
   "outputs": [],
   "source": []
  }
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